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Thread: Correlation test. Spearman's or Pearson's?

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    Unhappy Correlation test. Spearman's or Pearson's?




    Hello guys!
    I am a poor MA student trying to survive statistics!

    I have the following problem:

    The participants of a questionnaire were asked to rate the quality of

    a)education
    b)Intervention
    c)Support

    having as choices: not very useful, a little bit useful, useful , very useful.

    In the analysis, the authors turn these phrases in numbers from 1 to 4 and wanted to see if these 3 ratings were correlated.

    They used Pearson's correlation test.

    And my question is! Aren't these data ordinal? If yes, shouldn't they have used Spearman's test, which is suitable for ordinal data, while Pearson's is for interval/ratio?

    Thank you in advance!!

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    Re: Correlation test. Spearman's or Pearson's?

    Yes. This is commonly done, but Pearsons may not be the best choice here. Another relevant option is a polychoric correlation (correlation between the two variables, assuming that a normally distributed latent variable underlies each, with this latent variable disected into ordered categories by the rating scale).
    Matt aka CB | twitter.com/matthewmatix

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    Re: Correlation test. Spearman's or Pearson's?

    Depending on the data, from my limited experience, it may not matter if you run pearson, spearman, or polychoric, but its worth running all three and see how they differ. Unfortunately, unless you are using R, major software such as SPSS and SAS do not have polychoric analysis built into their system. SAS has a macro that does this, SPSS has an option to use R.
    "Very few theories have been abandoned because they were found to be invalid on the basis of empirical evidence...." Spanos, 1995

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    Re: Correlation test. Spearman's or Pearson's?

    Quote Originally Posted by noetsi View Post
    SPSS has an option to use R.
    Indeed, this is the best part of SPSS! Details on how to use it can be found here and here.
    Matt aka CB | twitter.com/matthewmatix

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    Re: Correlation test. Spearman's or Pearson's?

    Personally I don't think its is a very positive element of a software that they have to rely on another software to work
    "Very few theories have been abandoned because they were found to be invalid on the basis of empirical evidence...." Spanos, 1995

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    Re: Correlation test. Spearman's or Pearson's?

    Quote Originally Posted by noetsi View Post
    Personally I don't think its is a very positive element of a software that they have to rely on another software to work
    Look at the links I posted carefully
    Matt aka CB | twitter.com/matthewmatix

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    Re: Correlation test. Spearman's or Pearson's?


    Quote Originally Posted by CowboyBear View Post
    Look at the links I posted carefully
    LOL that was mean. At least you did not comment on SAS
    "Very few theories have been abandoned because they were found to be invalid on the basis of empirical evidence...." Spanos, 1995

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